1. Technical Field
The present invention relates generally to semiconductor fabrication, and more particularly, to methods for sealing an interlevel dielectric layer and metal layer.
2. Related Art
In semiconductor fabrication, processing requires two separate steps during generation of organic interlevel di-electric layers (ILDs) and metal layers in which the wafer is exposed to atmosphere including, for example, air, moisture, and possibly other chemicals. In particular, wafers are etched during via generation in such a way that organic ILD layers (e.g., SiLK by Dow Chemical) above the metal layer are opened and the metal layer is exposed to atmosphere when the wafer is moved between the etch chamber and deposition chamber for the metallization of the vias. In these instances, the organic ILD layers adsorb contaminants from the atmosphere, which can be later released during processing of upper levels where the wafer is exposed to thermal treatment. When these contaminants are released, they diffuse toward the weak interface of metal and dielectric, and create a resistive layer that hinders the electrical connectivity. In addition, contaminants can diffuse to the exposed metal interface of, for example, copper (Cu), and create an oxide layer. The oxide layer affects the electrical contact with the upper level metal.
In view of the foregoing, there is a need in the art for way to eliminate exposure of organic ILD (such as SiLK) and metal layers to any undesired atmosphere.